1. Field of the Invention
The present invention relates to a spindle motor rotational unbalance correction mechanism, and more specifically to a rotational unbalance correction mechanism for the spindle motor which turns the magnetic recording medium in a magnetic disk apparatus.
2. Description of Related Art
In a spindle motor that is used in a magnetic disk apparatus, to ensure highly reliable recording and playback of data, it is necessary to achieve extremely precise rotation.
Factors causing variation of the rotational precision of a spindle motor largely can be traced to two factors: machining accuracy and assembly accuracy, of elements used in the rotating system.
Of these factors, while the former, which are related to the accuracy of machining of the elements used, demand improvements in accuracy of machining during the manufacturing thereof, the latter factors, related to rotational unbalance, can be corrected either at the time of assembly or after assembly.
For example, there are methods for measuring the amount of rotational unbalance after assembly and then adding a counterbalance which cancels out this unbalance, thereby correcting the unbalance.
The methods of spindle motor unbalance correction used in a magnetic disk apparatus in the past, as noted above, relied on the spindle motor machining accuracy and/or on an adjustment operation performed at the time of assembly or after assembly.
However, with the trend toward higher accuracy in magnetic disk apparatuses, this approach becomes more and more difficult and is accompanied by an increase in cost.
An object of the present invention is to solve the above-noted problem by providing a spindle motor rotating system which is both low-cost and has good rotational balance, thereby achieving a magnetic disk apparatus which has high accuracy and a large storage capacity without only relying on an accuracy of machining and on an accuracy of assembling thereof.